U.S. patent number 5,105,644 [Application Number 07/550,303] was granted by the patent office on 1992-04-21 for light weight drive shaft.
Invention is credited to Joseph A. Simon.
United States Patent |
5,105,644 |
Simon |
April 21, 1992 |
Light weight drive shaft
Abstract
A lightweight driveshaft is extruded from a tubular metal blank
into an elongated tube having an integral center and opposite end
sections. The center section has a thin wall while the end sections
have a thick wall. The shaft is formed by inserting a tubular blank
within a tubular die having a restricted die throat through which
the blank is extruded. Punches are inserted into the tubular blank
to extrude the shaft.
Inventors: |
Simon; Joseph A. (Roseville,
MI) |
Family
ID: |
24196601 |
Appl.
No.: |
07/550,303 |
Filed: |
July 9, 1990 |
Current U.S.
Class: |
72/260 |
Current CPC
Class: |
B21C
23/14 (20130101); F16C 3/02 (20130101); B21K
1/10 (20130101); B21K 1/06 (20130101) |
Current International
Class: |
B21C
23/02 (20060101); B21K 1/76 (20060101); B21K
1/06 (20060101); B21K 1/00 (20060101); B21C
23/14 (20060101); B21K 1/10 (20060101); F16C
3/02 (20060101); B21C 023/08 () |
Field of
Search: |
;72/260,264,265 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
212808 |
|
Dec 1983 |
|
JP |
|
383300 |
|
Dec 1964 |
|
CH |
|
Primary Examiner: Larson; Lowell A.
Attorney, Agent or Firm: Harness, Dickey & Pierce
Claims
Having fully described such an operative embodiment, I now
claim:
1. A method for forming a light weight, elongated drive shaft which
may be used for the transmission of rotary power, such as in an
automotive vehicle and the like, comprising:
placing a tubular, metal blank having a lead end and a trailing end
within an open ended tubular die having an entry end through which
the blank is inserted for positioning within the die, and having an
outlet in the form of an annular, radially inwardly extending, die
throat of a smaller diameter than the blank outer diameter, with
the blank leading edge arranged adjacent the throat for extrusion
therethrough;
inserting a force applying punch, having an annular, relatively
blunt surface leading end, into the die entry end, with the punch
closely fitted within the die, and with the punch leading end
overlapping and engaging the trailing end of the blank, and with
the punch having a longitudinally aligned punch extension which
extends from said punch end, inserted into the blank tubular inner
opening for closely fitting within the opening, and arranging the
punch extension so that it extends from the blank trailing end
towards, but a predetermined distance inwardly of the blank, from
the leading end of the blank such that the extension is spaced from
the die throat;
moving the punch, with its extension, longitudinally relative to
the die, towards the die throat, a predetermined distance wherein
the punch extension remains spaced longitudinally inwardly from the
die throat, to extrude the leading end portion of the blank through
the die throat such that the extension is above the die throat and,
thereby, simultaneously collapse the leading end portion of the
blank radially inwardly so as to form said portion into a thick
wall tubular extruded section of a predetermined length which
corresponds to the punch extension remaining outwardly of the die
throat;
continuing moving the punch with its punch extension positioned
within and longitudinally moving within the die until the punch
enters the die throat and, thereafter, continuing such longitudinal
movement to extrude the corresponding blank portion into an
elongated, thin wall, predetermined length section;
stopping the punch movement upon completion of the extrusion of the
thin wall section, and retracting the punch and its extension from
the portion of the blank remaining within the die and outwardly of
the die, and inserting a second blank similar to the first blank,
into the die;
reinserting the punch into the die with its extension closely
fitted within the tubular inner opening of the second black, and
with the punch blunt end engaging the trailing end of the second
blank, so that the punch extension is arranged to extend from the
trailing end to substantially the same predetermined distance
longitudinally inwardly from the leading end of the second blank as
was used with the first blank;
longitudinally moving the punch to force the leading end of the
second blank against the trailing end of the first blank to extrude
the trailing end portion of the first blank followed by the leading
end portion of the second blank, through the die throat, while the
punch extension is spaced longitudinally inwardly above the die
throat to cause such first and second blank trailing end and
leading end portions respectively, to collapse radially inwardly as
they extrude through the die throat for forming thick wall sections
corresponding to the thick wall section formed on the leading end
portion of the first blank such that the thick wall sections are
about twice as thick as the thin wall sections;
continuing movement of the punch until the first blank is
completely extruded through the die throat by the moving second
blank such that the extension is completely within the second
blank, and then repeating the foregoing steps for continuously
producing extruded shafts; and
forming splines on the exterior of at least one of the thick wall
sections following the extrusion thereof.
2. A method as defined in claim 1, and including forming coupling
formations on the exterior of each of the thick wall sections of
the extruded drive shaft.
Description
BACKGROUND OF INVENTION
This invention relates to an improved drive shaft, such as is used
in transmitting power from an automotive engine to the wheels, and
more particularly, to a drive shaft of the same size and at least
of the same strength as a conventional drive shaft, but of
considerably lighter weight.
Drive shafts that are used in automotive vehicles for transmitting
the engine rotary power to the wheels, typically, are formed of a
solid, elongated, metal shaft having coupling formations formed on
its opposite ends. These may comprise splines or other suitable
couplings for connecting the ends of the shaft to the related
engine and wheel connecting parts. Conventional drive shafts, that
are used for front end drive vehicles, may be in the range of about
12 inches to about 36 inches, although the lengths vary
considerably. These shafts are usually manufactured by forging and
machining techniques and are relatively heavy. By way of example,
an approximately 27 inch long shaft of about 1 inch diameter weighs
about 5 pounds.
In recent times, in connection with fuel saving measures, vehicle
manufacturers have endeavored to lighten the weight of various
vehicle components. In the case of the power transmission shafts,
reducing the weight is difficult because of the strength
requirements and the manufacturing techniques used. Attempts have
been made to drill through the center of such a shaft, so that the
shaft is hollow, to reduce the weight, but this is relatively
expensive and tends to weaken the shaft. Thus, there is a need to
provide a manufacturing method to produce hollow, light weight
drive shafts which maintain the strength requirements normally
associated with solid shafts.
One manufacturing method for producing elongated tubes is cold
forming extrusion. This manufacturing process is described in my
U.S. Pat. No. 3,837,205 issued Sept. 24, 1974 for a "Process for
Cold Forming a Metal Tube With Inwardly Thickened End", U.S. Pat.
No. 3,886,649 issued June 3, 1975 for a "Process for Cold Forming a
Metal Tube With An Inwardly Thickened End", U.S. Pat. No. 4,277,969
issued July 14, 1981 for a "Method for Cold Forming Tubes Within
Interior Thicker Wall Sections" and U.S. Pat. No. 4,292,831 issued
Oct. 6, 1981 for a "Process for Extruding Metal Tube with Inwardly
Thickened End Portions". In addition, a similar process is
disclosed in my co-pending application, U.S. Ser. No. 07/490,286,
filed Mar. 8, 1990, now U.S. Pat. No. 4,991,421 granted Feb. 12,
1991, and relating to a Steering Gear Rack Type Device. The
invention herein is concerned with adapting the cold forming
extrusion process for manufacturing tubular drive shafts having
central sections formed with thinner walls than the end sections
for reducing the weight of the article while maintaining its
required performance strength and structural characteristics.
SUMMARY OF INVENTION
This invention contemplates extruding an integral elongated tubular
drive shaft having a central and two opposite end sections, with
the central section having a considerably thinner wall than the
opposite end sections. The added thickness of the end sections
provide the rigidity needed and also, the ability to form coupling
configurations, such as splines and the like at the ends of the
drive shaft. The thinner central section, provides sufficient
strength, but also some resiliency, for transmitting power and
absorbing rapid changes in the amount of power transmitted at any
particular moment, as well as to resiliently yield and absorb other
shock and vibratory forces.
The invention contemplates manufacturing the drive shaft by first,
forming a tubular blank having an interior opening which is close
to the interior diameter of the thin wall section of the drive
tube. The blank is positioned within a tubular die having a
constricted extrusion throat through which the blank is
extruded.
A power driven punch is inserted within the die. The punch has a
longitudinally extending extension which closely fits within the
opening in the blank, but does not extend the full length of the
blank. That is, it terminates at a predetermined distance from the
die throat. The punch pushes the blank toward the die throat so
that, first, the leading end of the blank is extruded through the
die throat to reduce its outer diameter and, simultaneously, to
collapse the material inwardly. This forms an inner, tubular
opening with a thick wall end section on the tube. By coordinating
the length of the extension and the dimensions of the blank, a
preselected length of thick wall tubing portion is formed.
Subsequently, as the punch moves towards the die throat, its
extension moves into the die throat and remains within the die
throat as the punch advances. During that time, further extrusion
of the blank results in the blank exterior diameter being extruded
to the required exterior diameter of the shaft. But the interior
diameter of the tube remains essentially the same as the diameter
of the blank and punch extension. This forms the long length, thin
wall center section of the drive.
Close to the end of the extrusion of the blank, the punch is
stopped and is completely removed. A new blank is placed within the
die and then the punch is reinstalled with its extension located
within the new blank. Then, movement of the punch towards the
throat presses the new blank against the trailing end portion of
the first blank. The pressure causes the completion of the
extrusion of that trailing end portion, while causing the leading
end portion of the second blank to extrude. This forms a thick wall
end section on the trailing end of the first blank and on the lead
end of the second blank.
When the first blank is completely extruded, it is removed and the
process is completed to continuously produce the tubes, blank by
blank.
One object of this invention is to provide a simplified procedure,
utilizing a single punch, to extrude an elongated tube. The tube
can be of considerable length, with elongated thick wall end
sections and a thin, lengthy center section. The sections will be
metallurgically similar due to the extrusion. Therefore, the ends
of the finished, extruded drive shaft may be heat treated or the
entire shaft may be heat treated, as required. For example, the
opposite ends may be heat treated to improve hardness and wear
resistance, etc.
Another object of this invention is to provide an inexpensive,
simplified procedure, for producing a high strength drive shaft
which is hollow so as to be considerably lighter than the
equivalent drive shafts conventionally used. For example, as
mentioned a 27 inch long, 1 inch diameter solid drive shaft may
weigh about 5 pounds, whereas the improved drive shaft of this
invention may weigh only about 3 pounds. Saving 2 pounds on the
product is a considerable weight reduction in the automotive
industry.
These and other objects and advantages of this invention will
become apparent upon reading the following description of which the
attached drawings form a part.
DESCRIPTION OF DRAWINGS
FIG. 1 is a cross sectional, schematic view of the extrusion blank
positioned within a die.
FIG. 2 is a cross sectional, schematic view showing the punch
located within the die and blank.
FIG. 3 is a schematic, cross sectional view showing the extrusion
of the lead portion thick wall section.
FIG. 4 is a schematic, cross sectional view showing the beginning
of the extrusion of the thin wall center section.
FIG. 5 is a schematic, cross sectional view showing the completion
of the extrusion of the thin wall, center section.
FIG. 6 schematically illustrates the removal of the punch following
the extrusion of the center section.
FIG. 7 schematically illustrates the positioning of the second
blank within the die and the positioning of the punch within the
die and second blank.
FIG. 8 schematically illustrates the completion of the extrusion of
the trailing end, thick wall section of the first blank and the
extrusion of the leading end portion of the second blank.
FIG. 9 schematically, and partially in cross section, illustrates
the removal of the extruded first blank and the continuation of the
extrusion of the second blank.
FIG. 10 is a perspective, partially cross sectional view of a
blank.
FIG. 11 is a perspective, partially cross sectional view of an
extruded drive shaft after the formation of splines on the
opposite, thick wall end sections.
FIG. 12 is a perspective view of a completed, splined, drive
shaft.
FIG. 13 is a cross sectional view of the drive shaft with the
splines formed on the opposite ends, and
FIG. 14 is an enlarged, cross sectional view showing the end
portion and part of the center portion of a drive shaft.
DETAILED DESCRIPTION
FIGS. 11-13 illustrate a light weight drive shaft 10 which is
formed with a thin wall, center section 11 and opposite, integral,
thick wall end sections 12 and 13. The extrusion process forms a
relatively large diameter, central opening 14 and smaller diameter
openings 15 in the opposite end sections 12 and 13. For example,
the end openings 15 may be about one half the diameter of the
central opening 14.
After the shaft is extruded, its opposite, thick wall ends, are
formed with coupling configurations or formations. By way of
example, the drawings show spline teeth 18 formed on the opposite
ends. However, the ends could be threaded or provided with other
configurations for coupling the opposite ends of the drive shaft to
the machine elements to which they are to be connected.
The process for manufacturing the drive shaft starts with a tubular
blank 20 (see FIG. 10) which has a central opening or hole 21. The
diameter of that hole is about equal to the intended diameter of
the interior of the thin wall center section 11.
The blank is dropped into a tubular die 25 through an open entry
end 26 in the die. The opposite end of the die is provided with a
constricted extrusion throat 27 provided by an annular, inwardly
extending shoulder 28.
After the blank is dropped into the die, a punch 30 is positioned
in the die. The punch has a lead end which is formed as an annular,
blunt surface 31 which overlaps and abuts the trailing end of the
blank. In addition, the punch has a punch extension 32 which is of
a diameter that approximates the diameter of the hole 21 in the
blank. Thus, the extension closely fits within the blank hole.
The punch extension is of a length that is slightly less than the
height of the blank, as illustrated in FIG. 2. Thus, its free end
is spaced longitudinally away from the die throat a short
distance.
FIG. 2 illustrates the blank positioned within the die and the
punch, with its punch extension 32, positioned relative to the
blank 30. Then, the punch is moved towards the die throat, as
illustrated in FIG. 3. This causes the leading end of the blank to
extrude through the die throat. As the end portion extrudes, it
collapses radially inwardly, leaving the central, smaller diameter
opening 15. During this time, the punch extension is located above,
that is, spaced from, the die throat.
As the punch continues movement towards the die throat, it
extension 32 enters the die throat. There, the punch extension acts
like a mandrel and the continued extrusion forms the thin wall,
center section of the shaft. As the die continues its movement, the
punch moves through the die throat, remaining within the die throat
as a mandrel, as shown in FIG. 5. At that point, the extrusion of
the thin wall, center section is complete.
Next, the punch is removed from the die, as shown in FIG. 6,
leaving the trailing end portion of the blank unextruded. Next, a
second blank 35, identical to the first blank, is dropped into the
die through its entry end. The same punch is replaced in position
within the die. Now, the punch abuts the second blank and its
extension extends into the opening in the second blank. Again, the
punch is moved toward the die throat so that the second blank acts
as the punch did in pushing the first blank through the die throat
for extruding it.
As shown in FIG. 8, the continued movement of the punch, with the
punch extension spaced longitudinally away from the die throat,
causes the trailing end portion of the first blank to extrude and,
simultaneously, collapse inwardly to form the thick wall end
section 13. Meanwhile, the lead end portion of the second blank is
extruded through the die throat and, likewise, collapses inwardly
to form the thick wall end extension 12.
Next, as illustrated in FIG. 9, the lead end of the second blank
continues extruding through the die throat, pushing the first blank
out of the die throat so that the extruded first blank may be
removed for forming the connection configurations on its ends.
The size of the drive shaft may vary considerably, depending upon
the particular intended use. By way of example, a drive shaft of
about 27 inches in length, 1 inch in diameter, with a larger
opening of 5/8 of an inch and a smaller opening of 1/4 inch, a thin
wall thickness of 3/16 of an inch and a thick wall thickness of 3/8
of an inch, and end sections which are 31/2 inches long, when made
of steel, weighs about 3 pounds. This contrasts with the 5 pound
weight of a drive shaft of the same size, but of solid
construction.
The hollow drive shaft, because of the extrusion of the metal is
strong enough to meet the requirements. Typically, such drive
shafts may have their opposite ends heat treated or otherwise
metallurgically improved, such as by nitriding, for increasing the
strength, toughness or wear resistance, depending upon the
requirements of the particular use.
The sizes of the shafts typically may range from 12 inch length to
36 inch lengths, with the diameter ranging between roughly 1 to 2
inches, and the lengths of the end sections ranging from 31/2 to
61/2 inches. Similarly, the wall thicknesses may vary from 1/8 inch
to 1/4 inch for the thin wall section with the thick wall being
roughly twice that thickness.
The foregoing description discloses an operative embodiment of this
invention. Accordingly, it is desired that the description be read
as being merely illustrative of an operative embodiment and not in
strictly limited sense.
* * * * *